The invention relates to labels for use on rubber products. In one aspect, the invention relates to labels comprising a polyester film while in another aspect, the invention relates to a label comprising a polyester film in combination with a primer for promoting adhesion of the label to a rubber substrate. In yet another aspect, the invention relates to methods of making and using such labels.
U.S. Pat. No. 5,709,918 to Kimijima and Sakashita, the disclosure of which is incorporated herein by reference, teaches an information-indicating label for use in the production of tires. The label consists essentially of a single layer polyester film substrate, e.g., polyethylene terephthalate (PET), in combination with a pressure sensitive adhesive, e.g., any of the natural or synthetic rubber-based adhesives. To promote the adhesive strength between the substrate and the pressure sensitive adhesive, a primer layer is included between the substrate and adhesive. Examples of appropriate primer layers include resorcinol-formaldehyde resin or resorcinol-formaldehyde latex resin.
While these labels are generally effective for their intended use, a demand remains for labels of this general construction but with an improved adhesiveness to rubber substrates, particularly green rubber such as tires prior to vulcanization.
According to this invention, a label comprising (i) a first primer layer of resorcinol-formaldehyde one side of which is in intimate contact with (ii) a film substrate, and the other side of which is in intimate contact with (iii) a pressure sensitive adhesive is improved by inserting between the film substrate and the primer layer (iv) a second primer layer comprising, in one embodiment, a condensation product of chlorophenol, resorcinol and a methylene donor, e.g., formaldehyde. The addition of this second primer layer significantly increases the peel adhesion of the label to a rubber substrate, particularly a green rubber substrate, e.g., a tire prior to vulcanization, at both ambient and elevated temperatures.